<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <style>
      #can{
          box-shadow: 1px 1px 5px 5px #ccc;/*居中*/
          position: absolute;/*定位*/
          top: 50%;
          left: 50%;
          transform: translate(-50%,-50%);/*转回去一点*/
      }

    </style>
</head>
<body>
<canvas id="can" width="450px" height="450px"></canvas>
<script type="application/javascript" src="ee.js"></script>
<script type="application/javascript" src="aa.js"></script>


</body>
</html>